Many women in labour end up with an unnecessary emergency caesarean section because they are in the care of a trainee obstetrician and not an experienced consultant, senior doctors claim today.

Much attention has been paid to what has been called the growth of the "too posh to push" phenomenon - women who ask for a caesarean because they do not want to undergo labour at all.

But there has also been a steady rise in the number of caesareans carried out as an emergency in the second stage of labour, when the baby should be progressing down the birth canal, says an article in the British Medical Journal - and some of them are not necessary.

"Although second stage caesarean section is sometimes appropriate, many could be prevented by the attendance of a more skilled obstetrician," says Chris Spencer, consultant obstetrician at St John's hospital, Chelmsford, in Essex.

The decision to carry out a caesarean is taken when labour does not seem to be progressing. The first option is usually for a doctor to attempt to deliver the baby using forceps or a ventouse - an instrument attached to the baby's head by suction.

The alternative is to carry out a caesarean. But, say the authors, consultant obstetricians can take substantially different views from trainees - specialist registrars - of when a caesarean is necessary.

A UK study found, they say, that "a consultant obstetrician who performed a vaginal assessment was more likely to reverse a decision made by an obstetric trainee for a caesarean and proceed to a safely conducted instrumental delivery".

From the woman's point of view, a successful vaginal birth makes labour seem worthwhile and is better for her health. There can be complications with caesareans: recovery from major surgery takes time, and it is less likely that the mother will have a normal birth next time, say the authors. But, they continue, "without increases in junior doctors' experience and recruitment into obstetrics, the problems with second stage caesareans will rise".

Sometimes, they say, the decision to go for surgery is made without any attempt to deliver the baby using instruments.

Around 35% of caesareans are performed because labour failed to progress, according to the Royal College of Obstetricians and Gynaecologists, and in more than half of those - 55% - "no attempt was made to achieve a vaginal birth with either forceps or ventouse".

Twin deliveries can lead to emergency caesareans, the authors say. Sometimes complications arise after the normal birth of the first baby - most commonly, the second is not in the right position or is in distress. Currently 10% of second twins are delivered by caesarean - but 10 years ago that rate was 5%, say the authors. "As many as two-thirds of these caesareans are preventable and are due to operator inexperience," they write.